1. Field of the Invention
The present invention relates to image forming devices, and more particularly, to an image forming device which has a power saving mode, as an operation mode, in which power consumption is saved.
2. Description of the Related Art
There is known an image forming device (such as a multi-function peripheral (MFP) provided with the scanner function, facsimile function, copying function, function as a printer, data communication function, and server function, a facsimile machine, a copier, a printer, and the like) which has the function of saving electric power by setting the operation mode to a power saving mode in which power supply to an image forming unit and the like is stopped.
There is also known an image forming device which has the authentication printing function (also referred to as “secure print”) which enables image formation only when authentication of a user (also referred to as “identity authentication”) has succeeded.
Document 1 below discloses an image forming device which controls driving of an operation panel in the power saving mode so as to restrict power consumption. In this image forming device, when a secure print instruction is accepted while the device is operating in the power saving mode, control of the operation panel is started. When the user performs an authentication operation via the operation panel, the power saving mode is released, and warming up is started. When the warming up is completed, printing is carried out. On the other hand, when a print instruction other than the secure print instruction is accepted while the device is operating in the power saving mode, the image forming device performs printing, without performing the control of the operation panel. Power consumption is thus restricted.    [Document 1] Japanese Patent Application Laid-Open No. 2004-152140
Warming up from the power saving mode may take some time, from several to several tens of seconds. For example, it is now assumed that in an electrophotographic image forming device, a non-contact thermistor is used to detect a temperature of a fixing device for control of the fixing device. In this case, detection of the temperature of the fixing device is not performed during the power saving mode, so as to save power. In order for the image forming device to enter a printable state from the power saving mode, it is necessary, firstly, to determine the temperature of the fixing device detected by the thermistor and, thereafter, to start driving the fixing device while referring to the detected temperature. A few seconds are required for the non-contact thermistor to determine the detected temperature of the fixing device.
With the image forming device as described in Document 1 above, in the case where a secure print instruction is received while the device is operating in the power saving mode, identity authentication is performed first, and then the power saving mode is released before the warming up is started. Thus, when the warming up requires a long time as described above, it will take a considerable time from when the identity authentication is performed until the warming up is finished. Such a long time required from the identity authentication till the printing out degrades convenience of the image forming device.
As a way of solving the above-described problem, it may be conceivable to cause the image forming device to release the power saving mode in the case where a secure print instruction is received while operating in the power saving mode. In this case, the warming up may be started earlier, resulting in a reduction in time required until the printing out. However, after the warming up is finished, the warmed state needs to be maintained until the end of the identity authentication process. This means that the power will be wasted if it takes some time before the identity authentication is completed.